THERMAL ENGINEERINGA. THERMODYNAMICES

PROF . SHEKHAR S. BABARMECHANICAL ENGINEERING DEPARTMENTICEM

THERMODYNAMICESTHERMO--- Heat Released

DYNAMICS ----- Mechanical Action For doing work The study of the effects of work, heat flow, and energy on a

system Movement of thermal energy Engineers use thermodynamics in systems ranging from

nuclear power plants to electrical components. Thermodynamics is the study of the effects of work, heat,

and energy on a system Thermodynamics is only concerned with macroscopic (large-

scale) changes and observations

SYSTEM, SURROUNDING ,UNIVERSE

SYSTEM-Area under thermodynamic study SURROUNDING – Area outside the system BOUNDARY- System & Surrounding are

separated by some Imaginary Or real Surface/Layer/Partition

UNIVERSE – System & Surroundings put together is called Universe

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ISOLATED, CLOSED AND OPEN SYSTEMS

Isolated SystemNeither energy nor mass can be exchanged.E.g. Thermo flask

ClosedSystemEnergy, but not mass can be exchanged.E.g. Cylinder filled with gas & piston

OpenSystemBoth energy and mass can be exchanged.E.g. Gas turbine, I.C. Engine

THERMODYNAMIC PROPERTIES

Thermodynamic Properties – It is measurable & Observable characteristics of the system.

Extensive: Depend on mass/size of system (Volume [V]), Energy

Intensive: Independent of system mass/size (Pressure [P], Temperature [T])

Specific: Extensive/mass (Specific Volume [v])

PRESSURE

P = Force/Area Pa, Kpa,Bar, N/m2

Types: Absolute Gage (Vacuum) Atmospheric

Pabs =Patm +/- Pgauge

PRESSURE PRESSURE

Volume

Three dimensional space occupied by an object

Unit- M3 , Liter1 m3 = 103 lit

Volume Volume

Temperature

Quantitative indication of Degree of Hotness & coldness of the body.

Unit- 0C , K , F Thermometer Thermometry

Temperature Temperature Scale

Internal energy

Internal energy (also called thermal energy) is the energy an object or substance is due to the kinetic and potential energies associated with the random motions of all the particles that make it up.

Internal energy is defined as the energy associated with the random, disordered motion of molecules.

Unit- KJ , Joule

Internal Energy Internal Energy [U]

Enthalpy

Total Heat content of Body Heat supplied to the body

Enthalpy increases & decreases when heat is removed

Enthalpy is a measure of the total energy of a thermodynamic system.

Enthalpy Enthalpy

Work Work = Force x Displacement (Nm) ( Joule) Energy in Transient Path function High grade energy Work done by the system on the surrounding -Positive workWork done on the system by surrounding – Negative work

HEAT Energy transfer by virtue of temperature difference Transient form of energy Path function Low grade energy Negative heat- heat transferred from the system ( heat rejection) Positive heat – heat transferred from surrounding to system (heat absorption)

HEAT Energy transfer by virtue of temperature difference Transient form of energy Path function Low grade energy Negative heat- heat transferred from the system ( heat rejection) Positive heat – heat transferred from surrounding to system (heat absorption)

HEAT CONCEPT

hot coldheat

26 °C 26 °C

Work & Heat

Work is the energy transferred between a system and environment when a net force acts on the system over a distance.

The sign of the work Work is positive when the

force is in the direction of motion

Work is negative when the force is opposite to the motion

WORK WORK

LAWS OF THERMODYNAMICS FIRST LAW OF THERMODYNAMICS (LAW OF ENERGY CONSERVATION) SECOND LAW OF THERMODYNAMICS ZEROTH LAW OF THERMODYNAMICS

Zeroth law of thermodynamics

FIRST LAW OF THERMODYNAMICS

CONSERVATION OF ENERGY ALGEBRAIC SUM OF WORK DELIVERED BY SYSTEM

DIRECTLY PROPOTOPNAL TO ALGEBRAIC SUM OF HEAT TAKEN FROM SURROUNDING

HEAT & WORK ARE MUTUALLY CONVERTIBLE NO MACHINE CAPABLE OF PRODUCING WORK

WITHOUT EXPENDITURE OF ENERGY TOTAL ENERGY OF UNIVERSE IS CONSTANT

LIMITATIONS OF FIRST LAW OF THERMODYNAMICS

Can’t give the direction of proceed can proceed- transfer of heat from hot body to cold body All processes involved conversion of heat into work & vice versa not equivalent. Amount heat converted into work & vice versa Insufficient condition for process to occurs

HEAT RESERVOIR, HEAT SOURCE, HEAT SINK HEAT RESERVOIR- Source of infinite heat energy & finite amount of heat addition & heat rejection from it will not change its temperature E. g. Ocean, River, Large bodies of water Lake HEAT SOURCE- Heat reservoirs which supplies heat to system is called heat source HEAT SINK- Heat reservoir which receives absorbs heat from the system

2ND LAW OF THERMODYNAMICSKELVIN –PLANCK’S STATEMENTIt is impossible to construct a machine which operates in cycle whose sole effect is to convert heat into equivalent amount of work

2ND LAW OF THERMODYNAMICSCLAUSIUS STATEMENT

It is impossible to construct a machine which operates in cycle whose sole effect is to transfer heat from LTB to HTB without consuming external work

CONCEPT STATEMENT

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2nd Law: Clausius and Kelvin Statements

Clausius statement (1850) Heat cannot by itself pass from a colder

to a hotter body; i.e. it is impossible to build a “perfect” refrigerator.

The hot bath gains entropy, the cold bath loses it. ΔSuniv= Q2/T2 – Q1/T1 = Q/T2 – Q/T1 < 0. Kelvin statement (1851) No process can completely convert heat

into work; i.e. it is impossible to build a “perfect” heat engine.

ΔSuniv= – Q/T < 0.1st Law: one cannot get something for nothing (energy

conservation).2nd Law: one cannot even break-even (efficiency must be

less than unity).

Q1 = Q2 = QM is not active.

HEAT ENGINEThermodynamic system/Device which operate in cycle converts the heat into useful work.

HEAT ENGINE HEAT ENGINE

HEAT ENGINE

Efficiency = e = W/Qs

hot

cold

hot

coldhot

hot QQ

QQQ

QWe

1

!!Kelvins!in measured be must res temperatuThe :Note

1hot

coldCarnot T

Te

HEAT PUMP Thermodynamic system/Device which operate in cycle converts the heat into useful work.

Cold Reservoir, TC

P

Hot Reservoir, THQH

QC

WORK

HEAT PUMP & REFRIGERATOR HEAT PUMP

Cold Reservoir, TC

RHot Reservoir, TH

QH

QC

W

Cold Reservoir, TC

PHot Reservoir, TH

QH

QC

W

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Reversible Engine: the Carnot Cycle Stage 1 Isothermal expansion at

temperature T2, while the entropy rises from S1 to S2.

The heat entering the system isQ2 = T2(S2 – S1).

Stage 2 adiabatic (isentropic) expansion at entropy S2, while the temperature drops from T2 to T1.

Stage 3 Isothermal compression at temperature T1, while the entropy drops from S2 to S1.

The heat leaving the system isQ1 = T1(S2 – S1).

Stage 4 adiabatic (isentropic) compression at entropy S1, while the temperature rises from T1 to T2.

Since Q1/Q2 = T1/T2, η = ηr = 1 – T1/T2.

POWER PLANT ENGINEERING

PROF. S. S. BABAR (MECHANICAL ENGG. DEPT)

POWER PLANT HYDROELECTRIC POWER PLANTTHERML POWER PLANTNUCLEAR POWER PLANTSOLAR POWER PLANTWIND POWER PLANTGEOTHERMAL POWER PLANTTIDAL POWER PLANT

THERMAL POWER PLANTCOMPONENTS 1. STEAM GENERATOR 2. STEAM TURBINE 3. GENERATOR 4. CONDENSER 5. FEED PUMP

THERMAL POWER PLANT

Cheaper fuels used Less space required Plant near the load centers so less transmission cost Initial investment is less than other plants

Plant set up time is more Large amount of water required Pollution Coal & ash handling serious problem High maintenance cost

ADVANTAGES DISADVANTAGES

HYDROELECTRIC POWER PLANT

HYDROELECTRIC POWER PLANT RESERVOIR DAM TRASH RACK GATE PENSTOCK TURBINE GENERATOR TAIL RACE

COMPONENTS HYDRO- ELECTRIC PLANT

HYDROELECTRIC POWER PLANT

HYDROELECTRIC POWER PLANT No fuel required No pollution Running cost low Reliable power plant Simple design & operation Water source easily available

Power depends on qty of water Located away from load center-transmission cost high Setup time is more Initial cost - high

ADVANTAGES DIS ADVANTAGES

NUCLEAR POWER PLANT

NUCLEAR POWER PLANT

NUCLEAR POWER PLANT

WPUI – Advances in Nuclear 2008

Fission controlled in a Nuclear Reactor

SteamGenerator

(HeatExchanger)

Pump

STEAM

Water

Fuel Rods

Control Rods

Coolant and Moderator

Pressure Vessel and Shield

ConnecttoRankineCycle

Large amount of energy with lesser fuels Less space No pollution Cost of power generation is less

Setup cost –more Availability of fuel Disposal of radioactive waste Skilled man power required Cost of nuclear reactor high High degree of safety required

ADVANTAGES DIS ADVANTAGES

NUCLEAR POWER PLANT

WIND POWER PLANT

WIND POWER PLANT AIR IN MOTION CALLED WIND KINETIC ENERGY OF WIND IS CONVERTED INTO MECHANICAL ENERGY K.E. = (M X V2 )/2 ROTOR GEAR BOX GENERATOR BATTERY SUPPORT STRUCTURE

WIND POWER PLANT

WIND POWER PLANT No pollution Wind free of cost Can be installed any where Less maintenance No skilled operator required

Low energy density Variable, unsteady, intermittent supply Location must be away from city High initial cost

ADVANTAGES DIS ADVANTAGES

SOLAR POWER PLANT

Freely & easily available No fuel required No pollution Less maintenance No skilled man power req.

Dilute source Large collectors required Depends on weather conditions Not available at night

ADVANTAGES DIS ADVANTAGES

SOLAR POWER PLANT

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